| Epoxy resin(EP)is widely used in gas insulated switchgear and gas insulated transmission line as insulating and strutting parts due to its excellent electrical and mechanical properties.However,in DC electric field,a large amount of electric charges are likely to accumulate on the interface between the epoxy resin and gas,which directly reduce the insulating performance and affect operation of the power system.In this paper,in order to improve the surface charge characteristics and enhance insulation performance,the low-temperture plasma is adopeed to modify the eposy resin.The physical morphology,chemical composition and electric properties of epoxy resin before and after modification are well studied.Firstly,the sub-atmospheric pressure glow discharge modification system is used for epoxy resin surface modification in air.The results show that the EP surface presents“mountain”like profile and a large number of hydrophilic groups such as C-O and C=O are detected after surface modification.The surface conductivity of EP increases approximately by one order of magnitude which is helpful for surface charge dissipation along the surface.The flashover voltage of the treated EP increases from-6.6 kV to-7.8kV which is increased by 17%.However,there is an obvious aging effect after surface modification.Secondly,the atmospheric pressure plasma jet and jet array are used for SiO_x thin film deposition on EP samples.The results show that a dense and homogeneous SiO_x film is depositied on EP surface.The main composition of film is Si containing inorganic groups(Si-O-Si and Si-OH).After treatment,the surface of samples is covered with a large number of nanoscale particles.The surface conductivity of EP increases approximately by 2.5 orders of magnitude.After film deposition,the depth of surface charge traps energy level is shallower and the density is smaller than that of pristine sample.In addition,the surface flashover voltage of epoxy resin increases by 46%.Further research is conducted on effect of nanosecond power parameters on the surface charge of epoxy resin before and after modification.This paper also illustrates the extent of impact of such as pulse frequency,pulse number,pulse rising time,pulse width,pulse falling time and pulse amplitude on the surface charge accumulation and disspation.The experimental results show that the accumulation of surface charge under nanosecond-pulse voltage presents a volcano-like profile and the accumulation of surface charge under the DC volatges appears like a mountain peak.Therefore,the impact of the amount and polar of the surface charge on the surface flashover are studied.The results show the surface charge both influences the electreci field strength and development process of surface discharge,which determins the surface discharge property.To sum up,low-temperture plasma can effectively improve the surface charge characteristics of epoxy resin and enhance its insulation performance.It provides scientific basis for solution of insulation problems of HVDC power transmission equipment. |
PDF Full Text Request